Memory is critical for mental health and proper cognitive functioning, but the ability to store and process information in short-term (working) memory is not well understood. Experiments of this application will use a popular working memory task (change-detection) to investigate object (what), location (where) and time (when) memory in pigeons, rhesus monkeys, and humans. We have developed procedures to train monkeys and pigeons to perform the same change-detection task (where one object changes at test) with the same memory arrays of objects at accuracies approaching those of humans. Animal studies will provide evidence about evolution of memory systems from a species (rhesus monkeys) comparatively closely related to humans and a species (pigeons) more distantly related. Species differences in language and neural architectures will provide evidence about the role of language and brain structures critical to these different types of memory under different testing conditions. Some conditions (blocked, large memory sets) will separate these different memory types;others will confound object and location memory (objects repeated in memory displays, and intermixing of object and location trials) or interfere with memory (repeating items from prior trials). Animals and humans may show similar memory results under conditions where memory types are separately tested and where performance depends more on sensory and bottom-up processing. Primates, particularly humans, are expected to perform best under conditions where interference or confounds must be resolved which depends more on top-down processing and the prefrontal cortex-the brain structure often considered most critical in cognitively separating primates (and other species). Human fMRI studies will determine activity-pattern differences when object and location memory are tested separately;conjunctions of object, location, and time memory;and proactive interference for time (when) memory. The results from these studies may lay the foundation for real-time recordings from monkey brain areas identified from the human fMRI studies and may help identify specific memory deficits in patients (e.g., PTSD) leading to better targeted treatment and evaluation. PUBLIC HEALTH RELEVANCE: Memory is critical to cognitive functioning and mental health and will be better understood by experiments of this application that will study memory for objects (what), locations (where) and time (when) with pigeons, rhesus monkeys, and humans to compare mechanisms of short-term memory and working memory. Species differences in language and neural architectures will provide evidence about the role of language and brain structures critical to these different types of memory and humans will be tested in an fMRI scanner to determine activity patterns and critical brain areas for different memory types and their conjunctions. Together these studies will lay the foundation for better understanding memory perhaps leading to real-time recordings from monkey brain areas identified from the human fMRI studies and better identification of specific memory deficits in patients (e.g., PTSD) for targeted treatment and evaluation.